Archives

Asphalt is about 5 percent oil. (http://blog.wired.com/cars/2008/05/blacktop-could.html)

http://www.cleanmpg.com/photos/data/501/Asphalt.jpgChuck Squatriglia - Wired - May 30, 2008

There are more than 4 million miles of paved road in the United States, and 93 percent of them are covered in asphalt. Unless you're backpacking in the wilds of Alaska or wandering the bayous of Louisiana, you are never more than 22 miles from a stretch of blacktop.

That's a lot of asphalt, and a lot of energy needed to produce it - which is why Hussain Bahia wants to find a greener way to make the stuff. He's a civil engineering professor at the University of Wisconsin-Madison, and he says anything that increases asphalt's recycled material content or cuts the energy needed to lay it down will have a big impact on the environment - and our pocketbooks.

"This is a no-brainer," says Bahia, who has been studying asphalt for more than 20 years. "If any person involved in managing our infrastructure looks at the data, why would you spend more energy and money on something else?"

Bahia is part of a $5 million research program called the Asphalt Research Consortium, which hopes to, among other things, make blacktop more ecologically sustainable. One of his first goals is to develop "cold-mix" asphalts that require significantly less energy than conventional asphalt to apply.

Asphalt is about 5 percent oil and 95 percent sand and rock; it's made from a black, sticky byproduct of oil refining. It's too thick to be applied without being heated to 300 degrees Fahrenheit. That requires a lot of energy, which is why other countries have been using cold-mix asphalts - also called emulsions - for years. One method involves shearing asphalt into fine particles, then mixing them with water and soap-like chemicals called surfactants that hold the asphalt in solution until its laid…http://blog.wired.com/cars/2008/05/blacktop-could.html

When the going gets expensive we look for alternatives! Why can't we look for alternatives BEFORE the world comes to an end????

My idea is make on of the lower layers recycled plastic and the upper layer recycled tires....maybe just partially.

There needs to be other alternatives to blacktops or blacktop alternatives. Here in south Louisiana, blacktop roads might stay in good shape for only 5 years after they are poured. It gets expensive replacing them...along with the front-end alignments due to all the pot holes in the blacktop.

There needs to be other alternatives to blacktops or blacktop alternatives. Here in south Louisiana, blacktop roads might stay in good shape for only 5 years after they are poured. It gets expensive replacing them...along with the front-end alignments due to all the pot holes in the blacktop.Just reminded me of my evening commute...a 1/4-mile after I get off I635 northbound to I35E, there is this pothole that had me wondering if it was going to bend rims....years ago it did on my 88 CRX HF :eek:

There needs to be other alternatives to blacktops or blacktop alternatives. Here in south Louisiana, blacktop roads might stay in good shape for only 5 years after they are poured. It gets expensive replacing them...along with the front-end alignments due to all the pot holes in the blacktop.

Among other things in my mis-spent youth I tested soils and concrete for a civil engineering firm. The road surface usually fails due to flaws in the paving subgrade. I'm guessing that Louisiana roads have an abundance of drainage issues that lead to widespread shrink/swell issues in the subgrade. Gravel and concrete are the common alternatives to asphalt but they have their own issues.

Chuck isn't the first one to think of putting used rubber in asphalt--it is already a common ingredient in asphalt seal coats. I doubt that most plastics have the right strength/temp stability characteristics to replace some of the aggregate in asphalt, but recycled glass is sometimes used to make "glassphalt".

Then putting glass beer bottles on the highway would be OK. :D

Bahia is part of a $5 million research program called the Asphalt Research Consortium, which hopes to, among other things, make blacktop more ecologically sustainable. One of his first goals is to develop "cold-mix" asphalts that require significantly less energy than conventional asphalt to apply.

We are doing some "cold-recycle" now: existing asphalt on a road is cored and analyzed. Desired changes in gradation are considered, along with desired asphalt content. A mix design is put into action. Loose stone is spread out on the road, a large milling machine/mixer comes along, mills up the existing asphalt pavement, mixing in the loose stone and adds asphalt emulsion, which is metered in. A paver spreads the new mix, it's compacted by rollers, and you have new pavement. It requires a top course of conventional hot-mix asphalt to seal it.

There is also warm-mix asphalt, which uses an additive to allow the hot-mix to be mixed and spread at a lower temperature.

http://www.warmmixasphalt.com/

Harry

Based on the smoke and smell alone, I've got to think that the toxic and smog-forming emissions from hot asphalt application are pretty nasty. Maybe these new processes reduce local pollutant emissions as well as GHG emissions?

Based on the smoke and smell alone, I've got to think that the toxic and smog-forming emissions from hot asphalt application are pretty nasty. Maybe these new processes reduce local pollutant emissions as well as GHG emissions?

Good point, asphalt is one of the top producers of smog-forming emissions. It would be interesting to see numbers. I don't live in a smoggy area--as a point of interest do they limit placement of new asphalt on bad air days?

Yes, a lot of the problems we have in south Louisiana is the surface that the road (be it asphalt or concrete) is layed upon. The road is only as good as the surface it is on. Asphalt cracks and crumbles leaving potholes. Concrete cracks also, but also buckles up in the heat creating speedbumps in the middle of the road (i.e. - and this is a real instance - at the onramp to the interstate). Or you might find where the start of multiple continuous sections of concrete have sunk and the ending part of the sections stay in tact leading to a "roller coaster" effect of a ride bouncing up and down the interstate (and yes, I have replaced my shocks!). Of coarse, Louisiana DOTD's fix for every is to either put a "Caution: Bump" sign or fill in potholes with asphalt 3 inches above the existing surface hoping cars will pack it down and until it is packed down, you are then left with a speed bump. And they wonder why there are so many wrecks here. Well, a lot has to do with people on cellphones (which there is currently a bill half way through our legislature to make it against the law to talk on cell phones and drive without a hands free device) and the poor conditions of our roads.

Good point, asphalt is one of the top producers of smog-forming emissions. It would be interesting to see numbers. I don't live in a smoggy area--as a point of interest do they limit placement of new asphalt on bad air days?I can't recall, but I think they do. Clean air action days only happen a couple times a year here, and I haven't noticed. Unlike many places, our worst air days come in the summer (i.e., the best time of year for laying asphalt) rather than the winter, so I'll try to take note this year.

Good point, asphalt is one of the top producers of smog-forming emissions. It would be interesting to see numbers.


I'd like to see the numbers, too, because I don't agree with you.

In New York, and probably most places, there are "bag houses" in all asphalt plants, to capture fumes and dust from producing hot-mix asphalt. Go by a plant producing hot mix, and you'll see a plume of white steam, the result of drying moisture from the sand and aggregates. There's no blue smoke, and almost no fumes. There might be a little smell if certain additives are used, like some types of liquid anti-strip.

Harry